A hydraulic retarder brake and a friction brake are important devices for braking large scale and other machines. The hydraulic retarder brake is used when heavy braking is required such as on descending a slope. Using a service brake alone may cause excessive heat generation in the friction portion of the service brake. Using the hydraulic retarder brake may decrease heat generation and thus prevent excessive wear or damage. The hydraulic retarder typically has a set of rotor blades, a set of stator blades, and a hydraulic fluid coupling. The rotor blades rotate with a wheel, the stator blades are fixed to a housing mounted on the machine, and the hydraulic fluid coupling between the opposing rotor blades and stator blades transmits the energy of rotating rotor blades to the circulating hydraulic fluid as heat due to the viscosity of the hydraulic fluid resulting in deceleration of the machine. Hydraulic retarder brakes may also be used with a transmission or a power train.
The friction brake is typically a disc brake that is engaged against all or certain wheels of the machine, such as the rear wheels, typically through a manual or automatic clutch when emergency stopping is required. Emergency friction braking for off highway machines may be designed to meet requirements for stopping based on grade, weight, location, and population.
Conventional braking system designs generally treat retarding and friction braking actions as separate and independent events that require two brake assemblies—a first brake assembly for providing the retarding action and a second brake assembly for providing the friction brake action. See, for example U.S. Pat. No. 4,235,320, which describes a retarder brake assembly and a friction brake assembly that are controlled according to schedules. These conventional braking systems are expensive because they require two separate brake assemblies. They take up more space because each brake assembly has an independent blueprint. Because they are separate braking systems they require a separate set of input controls by the operator. In addition, the efficiency of a brake system which combines a retarder brake assembly and a separate friction brake assembly is generally the sum of the efficiencies of each separate brake assembly part. There are little braking efficiencies that each separate brake assembly draws from the other brake assembly in performing braking action.
There is a need for a braking system that is less expensive, takes up less space, and is more efficient in delivering both retarder and friction braking action. This disclosure addresses this or other problems in the prior art.